Research On Digital Signal Analysis Based On LabWindows/CVI

All kinds of feature of digital signal are mainly researched in this paper. The signal is orthogonal-modulated, including MASK, MFSK, MSK, MPSK, PI/4_QPSK, QAM. By extracting the instantaneous amplitude, phase and frequency, and computing the very amplitude variance, mean frequency and phase variance, the modulation mode can be identified, compared to the gate value, and so does the multiple-amplitude-levels using the features. The methods of Time-Domain Analysis consist of eye diagram, vector diagram, constellation diagram, correlation, synchronization, etc. Of these, subtraction-clustering of clustering algorithm is used for recovering constellation diagram. Carrier and Clock Synchronization are introduced both in Time-Domain and Frequency-Domain, and also are simulated. The Transform-Domain Analysis includes Instantaneous Spectrum, Power Spectrum, Discrete Cosine Transform, Hilbert Transform, Wavelet Transform, etc. The Instantaneous Spectrum can be obtained by using window to observe the spectrum. Matlab functions are called to implement the Wavelet Analysis, including de-noising, feature extraction and reconstruction. Making use of the great power of Matlab in processing, filters are designed by calling Matlab commands via the interface of Labwindows/CVI.